1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly to a color filter array substrate and a fabricating method thereof.
2. Discussion of the Related Art
In general, liquid crystal display (LCD) devices use optical anisotropy and polarization properties of liquid crystal molecules to generate a desired image. In particular, liquid crystal molecules can be aligned in a specific orientation, which can be controlled by applying an electric field across the liquid crystal molecules. The liquid crystal display generally includes a liquid crystal display panel having liquid crystal cells arranged in a matrix-like manner and a driving circuit for driving the liquid crystal display panel.
In addition, the liquid crystal display panel also includes pixel electrodes for applying electric field to each of the liquid crystal cells and a reference electrode, i.e., a common electrode. Generally, the pixel electrode is formed on a thin film transistor (TFT) array substrate in the liquid crystal cells, and the common electrode is formed on another substrate, i.e., a color filter array substrate. Each of the pixel electrodes is connected to a TFT. Thus, the pixel electrodes along with the common electrode drive the liquid crystal cells to transmit light in accordance with a data signal supplied through the TFTs.
FIG. 1 is a perspective view illustrating a liquid crystal display panel according to the related art. In FIG. 1, a liquid crystal display panel includes a color filter array substrate 10 and a TFT array substrate 20 with a liquid crystal layer 8 formed therebetween. The color filter array 10 includes a black matrix 2, a color filter 4 and a common electrode 6. The color filter 4 includes color filters of red R, green G and blue B to transmit light of specific wavelength ranges, thereby displaying color lights. A black matrix 2 is formed between adjacent color filters 4 to absorb the light incident from the adjacent cells, thereby preventing a color contrast from being deteriorated.
The TFT array substrate 20 includes data lines 18 and gate lines 12 intersecting each other, thereby defining a plurality of cell areas. A gate insulating film (not shown) is formed between the data lines 18 and the gate lines 12. A TFT 16 is formed at each intersection between the data lines 18 and gate lines 12. In particular, the TFT 16 includes a gate electrode connected to a respective one of the gate lines 12, a source electrode connected to a respective one of the data lines 18, and a drain electrode facing the source electrode with a channel part that includes an active layer and an ohmic contact layer. The TFT 16 is electrically connected to the pixel electrode 14, such that the TFT 16 responds to a gate signal from the respective gate line 12 to selectively supply the data signal from the respective data line 18 to the pixel electrode 14.
The pixel electrode 14 is located at each of the cell areas and includes a transparent conductive material having high light transmissivity. The pixel electrode 14 generates a potential difference with the common electrode 6 by the data signal supplied through the drain electrode of the TFT 16. The potential difference causes the liquid crystal layer 8 to rotate by dielectric constant anisotropy. Accordingly, the light incident on the liquid crystal panel from a light source (not shown) is transmitted in accordance with the data signal.
Each pixel includes three sub-pixels realizing red color R, green color G, and blue color B. However, poor brightness is generated by these R, G, B sub-pixels because the amount of light being transmitted to the upper substrate 1 through the color filter 4 generally is only about 27˜33% of the amount of light generated by a backlight. In order to solve this problem, a color filter array substrate of a liquid crystal display panel shown in FIG. 2 has been proposed.
FIG. 2 is a cross-sectional view illustrating a color filter array substrate having a white color filter according to the related art. As shown in FIG. 2, a color filter array substrate includes a pixel having four sub-pixels realizing red color R, green color G, blue color B and white color W. In particular, the amount of light being transmitted through the W sub-pixel generally is not less than 85% of the amount of light generated by the backlight unit. Accordingly, the overall amount of light being transmitted through the R, G, B, W sub-pixels is higher, thereby improving brightness of the liquid crystal display panel.
FIGS. 3A to 3G are cross-sectional views illustrating a fabricating method of the color filter array substrate shown in FIG. 2. As shown in FIG. 3A, an opaque material is deposited on the entire surface of the upper substrate 1. The opaque material includes opaque metal or opaque resin, e.g., chrome (Cr). The opaque material then is patterned by a photolithography process and an etching process using a first mask (not shown) to form a black matrix 2.
As shown in FIG. 3B, a red resin is deposited on the entire surface of the upper substrate 1 over the black matrix 2. The red resin then is patterned by the photolithography process using a second mask (not shown) to form a red color filter 4R. In addition, as shown in FIG. 3C, a green resin is deposited on the entire surface of the upper substrate 1 over the black matrix 2 and the red color filter 4R. The green resin then is patterned by the photolithography process using a third mask (not shown) to form a green color filter 4G. Further, as shown in FIG. 3D, a blue resin is deposited on the entire surface of the upper substrate 1 over the black matrix 2, the red color filter 4R and the green color filter 4G. The blue resin then is patterned by the photolithography process using a fourth mask (not shown) to form a blue color filter 4B.
Then, as shown in FIG. 3E, a white resin is deposited on the entire surface of the upper substrate 1 over the black matrix 2, the red color filter 4R, the green color filter 4G and the blue color filter 4B. The white resin includes acrylic resin. The white resin then is patterned by the photolithography using a fifth mask (not shown) to form a white color filter 4W.
Further, as shown in FIG. 3F, an organic insulating material including the same material as the white resin is deposited on the entire surface of the upper substrate 1 over the black matrix 2, the red color filter 4R, the green color filter 4G, the blue color filter 4B and the white color filter 4W. The organic insulating material then is patterned by the photolithography process using a sixth mask (not shown) to form an overcoat layer 22.
Moreover, an organic insulating material including the same material as the overcoat layer 22 is deposited on the entire surface of the upper substrate 1 over the black matrix 2, the red color filter 4R, the green color filter 4G, the blue color filter 4B, the white color filter 4W and the overcoat layer 22. The organic insulating material then is patterned by the photolithography process using a seventh mask (not shown) to form a spacer 24.
Thus, the fabricating method of the color filter substrate for the LCD device according to the related art requires at least seven mask processes or photolithography processes to form the color filter substrate including the black matrix, the red, green, blue and white color filters, the overcoat layer and the patterned spacer. Since a mask used in each of the mask processes is very expensive, a production cost is increased and a fabricating process is complicated, thereby reducing production efficiency.